John Deere 500c Backhoe fuel in oil after sitting.

[TreeZ]

In the summer I topped up the fuel tank in my 1974 John Deere 500c Backhoe. It sat for two months, then I fired it up. Liquid gushed out of crank case vent. Shut off tractor, oil level was way high. I drained 5 gal of diesel/oil mixture out of oil pan just to get liquid within range on dip stick. Diesel in fuel tank was 5 gal lower than when I filled it.
How does fuel drain into oil pan when it isn't running?
According to spec sheet this is a "300 series" engine.
Otherwise, engine runs fine with no smoke.

 

[beenthere]

TreeZ
Welcome to TBN
Interesting problem. Good question for members here.

 

[thepumpguysc]

That’s an easy one..
If u didn’t shut the fuel off at the petcock under the tank,
GRAVITY took control and made it past the seals on the drive shaft in the inj pump and filled the oil pan with fuel.
You could also have a grooved “pilot tube” in the front of the inj pump where the rubber seals ride..
It’s a VERY COMMON PROBLEM..

 

[Tx Jim]

Welcome to this forum
I'd start by checking/replacing fuel transfer pump. Transfer pump part # is RE37482. If that didn't solve fuel in engine crankcase then R&R seals on inj pump drive shaft that thepumpguysc recommended. FYI JD 500C doesn't have a 300 series engine but has same engine as JD 3010 & 3020 rowcrop tractors IE 270 CID(4.4L) which BTW are fairly rare compared to other JD 4 cylinder engines. JD 300 series engines were manufactured for utility tractors in the Mannheim or Saran factories while 500C engines were manufactured in the USA.

 

[thepumpguysc]

I forgot about the supply pump..
Good catch Tx Jim..

 

[TreeZ]

That’s an easy one..
If u didn’t shut the fuel off at the petcock under the tank,
GRAVITY took control and made it past the seals on the drive shaft in the inj pump and filled the oil pan with fuel.
You could also have a grooved “pilot tube” in the front of the inj pump where the rubber seals ride..
It’s a VERY COMMON PROBLE

Surprisingly the fuel line didn't have a petcock. That was my first assumption so installed an in line valve that I had laying around. Still getting diesel in oil. Even with valve... maybe need better one.
I should replace fuel line with better one and install better metal shut off valve right at tank end. If that doesn't do it look at injector pump.

 

[TreeZ]

Welcome to this forum
I'd start by checking/replacing fuel transfer pump. Transfer pump part # is RE37482. If that didn't solve fuel in engine crankcase then R&R seals on inj pump drive shaft that thepumpguysc recommended. FYI JD 500C doesn't have a 300 series engine but has same engine as JD 3010 & 3020 rowcrop tractors IE 270 CID(4.4L) which BTW are fairly rare compared to other JD 4 cylinder engines. JD 300 series engines were manufactured for utility tractors in the Mannheim or Saran factories while 500C engines were manufactured in the USA.

Thanks for the welcome

The fuel transfer pump was replaced by pervious owner one year ago. Not sure the reason why, or what happened to old one. It's the silver piece in this pic that he replaced.

Or like I said to Thepumpguysc, maybe Install better petcock and perhaps the rest wouldn't matter. Well, only if fuel is bypassing plastic valve while engine is off. If it is making oil while running will certainly have to dig further into lift pump or injection pump. I haven't wanted to run it to find out with diesel in oil.

 

[TreeZ]

A couple more pics for reference..

 

[TreeZ]

Pics

 

[Tx Jim]

Fuel line shut-off valve if operating correctly should stop fuel from entering engine crankcase while engine is setting idle IE not operating BUT valve will have no affect on the problem while engine is operating. In today's world of "almost right parts" I would be checking transfer pump to determine if it was the cause of fuel in crankcase. Another option is just disconnecting fuel transfer pump & installing an electric fuel in it's place. If it wasn't the cause then R&R umbrella seals on inj pump shaft. You definitely don't want engine oil thinned by diesel destroying your engines crankshaft bearings!!!!!!!!!